Liliane Krespi | Rennes 1 (original) (raw)

Papers by Liliane Krespi

Ethology Ecology & Evolution, 2004

In this paper, we compare the host selection behaviours of two parasitoids, Aphidius rhopalosiphi... more In this paper, we compare the host selection behaviours of two parasitoids, Aphidius rhopalosiphi and Aphidius picipes, in order to analyse whether behavioural adaptations to the defensive behaviour of their host (the grain aphid Sitobion avenae) could, in part, be responsible for the simultaneous presence of both species in cereal fields.The oviposition behaviour of A. picipes differed from that of

Microscopy Research and Technique, 2006

sensilla ABSTRACT Several species of the genus Aphidius are used in biological control programs a... more sensilla ABSTRACT Several species of the genus Aphidius are used in biological control programs against aphid pests throughout the world and their behavior and physiology are well studied. But despite knowing the importance of sensory organs in their behavior, their antennal structure has never been described. We describe here the types and distribution of antennal sensilla in Aphidius rhopalosiphi, a

Biocontrol, 2000

Journal of Insect Behavior, 2000

Host rejection, superparasitism, and ovicide are three possible host selection strategies that pa... more Host rejection, superparasitism, and ovicide are three possible host selection strategies that parasitoid females can adopt when they encounter parasitized hosts. These differ in costs (in terms of time and energy required) and benefits (in terms of number and quality of offspring produced). Their relative payoff should vary with patch quality, (i.e., proportion of parasitized hosts present), and female choice between them should be adapted accordingly. We conducted behavioral observations to test the effect of the ratio of parasitized/unparasitized hosts present in a patch on the host selection strategies of Pachycrepoideus vindemmiae Rondani (Hymenoptera: Pteromalidae). This species being a generalist known to attack hosts of a great range of size, we also tested the impact of host size on female decisions with two host species differing greatly in size (Drosophila melanogaster and Delia radicum). We evaluated the adaptive value of each strategy in relation to host parasitization status and host size by measuring their duration and the potential number of offspring produced.

Environmental Entomology, 2004

In solitary parasitoid species, superparasitism incurs a high cost because only one individual ca... more In solitary parasitoid species, superparasitism incurs a high cost because only one individual can emerge per host. While avoiding already-parasitized hosts seems advantageous, it requires an ability to discriminate between parasitized and unparasitized hosts. The ability to discriminate can be based on physical or chemical cues or signal associated either internally or externally with a given host. The type of stimuli used to recognize parasitized hosts generally depends on the features of these hosts but also on costs and beneÞts associated with reusing them. Some local factors such as mortality rate of females, host availability, and competition level can inßuence this trade-off. In species that occupy a large geographic range, local conditions may favor either external or internal mechanisms of host discrimination. We describe the behaviors associated with host discrimination in Pachycrepoideus vindemmiae Rondani (Hymenoptera: Pteromalidae), a solitary pupal parasitoid of cyclorraphous dipteran species. To detect potential intraspeciÞc variability in their host discrimination behavior, we compared two P. vindemmiae populations originating from different geographical areas in France. Our results revealed different host discrimination strategies in both populations and indicated a potential trade-off between the speed and the accuracy of host discrimination. One population discriminated hosts externally (faster but less accurately), whereas the other discriminated internally (more slowly but more accurately). In our experimental conditions, these two strategies resulted in differences in the Þtness gains of both populations. The ecological conditions that could have selected for such differences in the host discrimination and oviposition strategies of the two populations remain to be investigated.

Entomologia Experimentalis et Applicata, 2002

Although hyperparasitism frequently occur in parasitic insects, many aspects of this strategy rem... more Although hyperparasitism frequently occur in parasitic insects, many aspects of this strategy remain unknown. We investigated possible fitness costs of hyperparasitism as influenced by host size. Our study was conducted with the facultative hyperparasitoid Pachycrepoideus dubius Ashmead (Hymenoptera: Pteromalidae), which parasitizes host species differing greatly in size. We compared some fitness traits (level of successful parasitism, development time, sex ratio and offspring size) of P. dubius developing on large secondary / primary (Delia radicum L. (Diptera: Anthomyiidae)/ Trybliographa rapae Westwood (Hymenoptera: Figitidae)) or small secondary / primary host species (Drosophila melanogaster L. / Asobara tabida Nees (Hymenoptera: Braconidae)). In no-choice and choice experiments, P. dubius was able to develop on different stages of T. rapae (L2 (endophagous), L4 (ectophagous), and pupae) but that it preferred to parasitize unparasitized D. radicum pupae over pupae parasitized by T. rapae. Furthermore, in P. dubius, hyperparasitism was associated with fitness costs (lower level of successful parasitism, smaller adult size) and these costs were greater on the smallest host complex. We hypothesize that the size of D. melanogaster pupae parasitized by A. tabida may be close to the suboptimal host size for P. dubius beneath which the costs of hyperparasitism make this strategy nonadaptive. Hyperparasitism in terms of trade-offs between host quality and abundance of competitors is discussed.

Entomologia Experimentalis et Applicata, 2013

Organisms can either evade winter's unfavourable conditions by migrating or diapausing, or endure... more Organisms can either evade winter's unfavourable conditions by migrating or diapausing, or endure them and maintain their activities. When it comes to foraging during winter, a period of scarce resources, there is strong selective pressure on resource exploitation strategy. Generalist parasitoids are particularly affected by this environmental constraint, as their fitness is deeply linked to the profitability of the available hosts. In this study, we considered a cereal aphid-parasitoid system and investigated (1) the host-parasitoid community structure, host availability, and parasitism rate in winter, (2) the influence of host quality in terms of species and instars on the fitness of the aphid parasitoid Aphidius rhopalosiphi De Stefani-Perez (Hymenoptera: Braconidae: Aphidiinae), and (3) whether there is a detectable impact of host fidelity on parasitism success of this parasitoid species. Host density was low during winter and the aphid community consisted of the species Rhopalosiphum padi L. and Sitobion avenae Fabricius (both Hemiptera: Aphididae), both parasitized by A. rhopalosiphi at non-negligible rates. Aphidius rhopalosiphi produced more offspring when parasitizing R. padi compared with S. avenae, whereas bigger offspring were produced when parasitizing S. avenae. Although aphid adults and old larvae were significantly larger hosts than young larvae, the latter resulted in higher emergence rates and larger parasitoids. No impact of host fidelity on emergence rates or offspring size was detected. This study provides some evidence that winter A. rhopalosiphi populations are able to take advantage of an array of host types that vary in profitability, indicating that host selectivity may drop under winter's unfavourable conditions.

Bulletin of Entomological Research, 2009

Three related Aphidius parasitoid species share the same host, the grain aphid Sitobion avenae. A... more Three related Aphidius parasitoid species share the same host, the grain aphid Sitobion avenae. Among this parasitoid community, Aphidius rhopalosiphi is the most abundant species in the field. Both the interspecific host discrimination of A. rhopalosiphi towards hosts parasitized by the two other species (i.e. A. avenae and A. ervi) and the interspecific host discrimination of the two other species towards hosts parasitized by A. rhopalosiphi were studied here. Results showed that females of A. rhopalosiphi and A. avenae both discriminated between unparasitized hosts and hosts parasitized by the other species. This discrimination occurred only after ovipositor insertion, suggesting the perception of an internal marker of parasitism. Likewise, females of A. rhopalosiphi and A. ervi were able to discriminate between unparasitized hosts and hosts parasitized by the other species. However, in this combination of species, recognition of parasitized hosts occurred before ovipositor insertion, through an antennal perception, suggesting the presence an external cue indicating parasitism. Hence, interspecific host discrimination in the three Aphidius species is based on internal or external cues, which are used either alone or together. Our results showed that the cues used for interspecific host discrimination depend on the specific identity of the interaction. These differences seemed strongly linked to the way the different species respond to defensive behaviours of their aphid hosts. Results are discussed in the context of optimal foraging and possible consequences for community structure.

BioControl, 2012

Cold storage of insect parasitoids is currently used before mass release in the field in biologic... more Cold storage of insect parasitoids is currently used before mass release in the field in biological control programmes. The physiological consequences of constant cold storage are known in various species of parasitic wasps, but there are few reports on the behaviour of survivors and even fewer reports where both sexes were tested. In this study, we observed the consequences of a long storage of Aphidius rhopalosiphi De Stephani Perez (Hymenoptera: Braconidae), a parasitoid of the cereal aphid Sitobion avenae Fabricius (Hemiptera: Aphididae), at low temperature on some key behavioural decisions that both sexes will make when released in the field. Males are less tolerant than females and both sexes suffer from a long exposure (28 days or more) at 4°C during the pupal stage: alteration of olfactory responses, decrease in mating capacity and decrease in the efficiency of patch exploitation by females.

Ecological Entomology, 2008

Abstract 1. In solitary parasitoids, several species can exploit the same host patch and competit... more Abstract 1. In solitary parasitoids, several species can exploit the same host patch and competition could potentially be a strong selective agent as only one individual can emerge from a host. In cereal crops, Aphidius rhopalosiphi and A. ervi share the grain aphid Sitobion avenae as host.2. The present work studied foraging strategies of both species on patches already exploited by the other species. The study analysed larval competition in multi-parasitised hosts and compared the foraging behaviour of females with and without previous experience.3. It was found that A. ervi wins larval competition three times more often than A. rhopalosiphi. Both species spent less time on patches exploited by a heterospecific than on unexploited ones. When they foraged on heterospecifically exploited patches, experienced females induced less mortality in aphids than inexperienced ones.4. Although A. rhopalosiphi is a specialist on cereal aphids and is the most abundant species due to its early appearance in the season, S. avenae is still a profitable host for A. ervi, because: (i) A. rhopalosiphi leaves patches partially exploited, (ii) A. ervi wins larval competition in three out of four multi-parasitised hosts, and (iii) A. ervi is only slightly deterred by the cornicular secretions of the host and can thus easily parasitise hosts.